Methods of using acrylate-containing polymer blends

ABSTRACT

A method of priming a substrate comprising applying to the substrate a blend comprising (a) a modified block copolymer comprising (i) a polystyrene block and (ii) a polydiene block or a hydrogenated polydiene block, the polydiene block or hydrogenated polydiene block being modified to contain an average of one or more carboxyl groups; and (b) a polymer comprising a polymerization reaction product of two or more mono-ethylenically unsaturated monomers in which (i) at least one of the monomers is an acrylic or methacrylic acid ester of a non-tertiary alcohol having 1 to 14 carbon atoms, inclusive, and (ii) at least one of the monomers is a nitrogen-containing monomer; in particular, a method of enhancing adhesion between a substrate and an adhesive comprising the steps of priming the substrate by applying to the substrate the blend and applying the adhesive to the primed substrate.

This is a continuation-in-part application of U.S. Ser. No. 08/361,058,filed Dec. 21, 1994 (now abandoned in favor of U.S. Ser. No. 08/589, 198filed Jan. 22, 1996), which is a continuation-in-part of 08/182,573,filed Jan. 14, 1994, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to polymer blends useful, e.g., as adhesives,primers, inks, and paints.

2. Description of the Background Art

Low surface energy substrates such as polyethylene, polypropylene, andother polyolefins are characterized as having critical surface tensionsof wetting of about 35 dynes/cm or less. Such surfaces are generallyunreceptive to inks, paints, and adhesives due to their poorwettability. There is a need to improve adhesion to such surfaces, aswell as to high energy surfaces.

SUMMARY OF THE INVENTION

The present invention relates to a method of priming a substratecomprising applying to the substrate a blend comprising (a) a modifiedblock copolymer comprising (i) a polystyrene block and (ii) a polydieneblock or a hydrogenated polydiene block, said polydiene block orhydrogenated polydiene block being modified to contain an average of oneor more carboxyl groups; and (b) a polymer comprising a polymerizationreaction product of two or more mono-ethylenically unsaturated monomersin which (i) at least one of the monomers is an acrylic or methacrylicacid ester of a non-tertiary alcohol having 1 to 14 carbon atoms,inclusive, and (ii) at least one of the monomers is anitrogen-containing monomer.

In particular, the present invention also relates to a method ofenhancing adhesion between a substrate and an adhesive comprising thesteps of priming said substrate by applying to said substrate a blendcomprising (a) a modified block copolymer comprising (i) a polystyreneblock and (ii) a polydiene block or a hydrogenated polydiene block, saidpolydiene block or hydrogenated polydiene block being modified tocontain an average of one or more carboxyl groups; and (b) a polymercomprising a polymerization reaction product of two or moremonoethylenically unsaturated monomers in which (i) at least one of themonomers is an acrylic or methacrylic acid ester of a non-tertiaryalcohol having 1 to 14 carbon atoms, inclusive, and (ii) at least one ofthe monomers is a nitrogen-containing monomer; and applying an adhesiveto the primed substrate. In some preferred embodiments, the substrate isa low energy substrate. As used herein, "low energy substrate" refers toa substrate having a critical surface tension of wetting no greater thanabout 35 dynes/cm. Examples include polyolefin polymers such aspolyethylene and polypropylene.

The invention provides polymer blends that exhibit good adhesion to bothlow energy surfaces (e.g., polyolefins such as polyethylene andpolypropylene), as well as higher energy surfaces (i.e., having surfaceenergies greater than 35 dynes/cm such as metal and glass). The blendsare useful as primers (e.g., for paints and coatings), adhesives (e.g.,for use as tie layers), pressure sensitive adhesives, inks, and paints.

DETAILED DESCRIPTION OF THE INVENTION

The invention features blends comprising a modified block copolymer (a)and an acrylate or methacrylate ester-containing polymer (b) as setforth in the Summary of the Invention section.

The block copolymer comprises one or more polystyrene blocks. If one ortwo polystyrene blocks are present, the block copolymer can bedesignated as an AB block copolymer (containing one polystyrene block)and an ABA block copolymer (containing two polystyrene blocks), "A"designating polystyrene and "B" designating polydiene or hydrogenatedpolydiene.

Examples of a polydiene block or hydrogenated polydiene block include,e.g., a polybutadiene, polyisoprene, ethylene/butylene, orethylene/propylene block. The term "polydiene" refers to repeating unitsof a diene monomer. The hydrogenated polydiene block preferably has aresidual unsaturation of less than 10%, more preferably less than 5%,based on the original amount of ethylenic unsaturation of the polydieneblock. Examples of compounds which may be reacted with the polydieneblock or the hydrogenated polydiene block to provide the substituentcarboxyl groups include carboxylic acids and anhydrides (e.g., maleicacid and maleic anhydride).

A particularly preferred block copolymer is a maleatedstyrene-ethylene/butylene-styrene block copolymer. The term "maleated"means that the polydiene or hydrogenated polydiene block is modified,for example, with maleic acid or maleic anhydride so that the polydieneor hydrogenated polydiene block contains an average of one or morecarboxyl groups. An example of a preferred polymer is astyrene-ethylene/butylene-styrene triblock copolymer containing 2% byweight succinic anhydride (the source of the carboxyl groups)(commercially available from Shell Chemical Company, Houston, Tex.,under the trade designation "Kraton FG-1901X"). "Kraton FG-1901X" has atensile strength of about 5000 psi, a percent elongation of about 500, aShore A hardness of about 75, a specific gravity of about 0.91, and aBrookfield viscosity of about 1250 cps at 77° F. (25° C.).

Block copolymer (a) has a ratio, by weight, of polystyrene block topolydiene block or hydrogenated polydiene block typically ranging fromabout 5:95 to 95:5, more preferably 10:90 to 50:50.

Polymer (b) is the polymerization reaction product of two or moremonoethylenically unsaturated monomers in which (i) at least one of themonomers is an acrylic or methacrylic acid ester of a non-tertiaryalcohol having 1 to 14 carbon atoms, inclusive, and (ii) at least one ofthe monomers is a nitrogen-containing monomer.

In addition, polymer (b) may further comprise component (iii), i.e., amonomer having at least one of carboxylic acid functionality, hydroxyfunctionality, and epoxy functionality or combinations of thesemonomers. Examples of monomer (iii) includes acrylic acid, methacrylicacid, itaconic acid, 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, glycidyl acrylate, and glycidyl methacrylate. Acrylic andmethacrylic acid are preferred. The amount of component (iii), whenpresent, is preferably 1 to 10 parts by weight, more preferably 1 to 5parts by weight, based on 100 parts by weight of polymer (b). In anycase, polymer (b) comprising components (i) and (ii), or (i), (ii), and(iii) is not crosslinked.

The non-tertiary alcohol preferably includes methanol, ethanol,1-propanol, 2-propanol, 1-butanol, 1-pentanol, 2-pentanol, 3-pentanol,2-methyl-1-butanol, 1-methyl-1-butanol, 1-methyl-1-pentanol,2-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol,3,5,5-trimethyl-1-hexanol, 3-heptanol, 2-octanol, 1-decanol, or1-dodecanol. A particularly preferred ester monomer is iso-octylacrylate.

The nitrogen-containing monomer may comprise an N-vinyllactam (e.g.,N-vinylpyrolidone or N-vinylcaprolactam), acrylamide, anN-alkylacrylamide (e.g., N-methylacrylamide), an N,N-dialkylacrylamide(e.g., N,N-dimethylacrylamide), or combinations thereof . The amount ofnitrogen-containing monomer depends on the monomer selected. Typically,the amount of nitrogen-containing monomer is at least 2 parts by weight,preferably 5 parts to 40 parts by weight, based on 100 parts by weightof polymer (b). For example, 5 to 30 parts by weight of anitrogen-containing monomer is preferred when N-vinyllactams andN,N-dimethylacrylamides are used individually. In addition, at least 5parts by weight of acrylamide is typical when used alone; however, if anN-vinyllactam and acrylamide are used together, the amount of acrylamideused can be less than 5 pans by weight, for example, 1 to 4 parts byweight. The nitrogen-containing monomer of the present invention doesnot contain acrylic and methacrylic acid ester groups, as in the case ofN-vinyllactams, but may contain acrylic or methacrylic acid orderivatives thereof , as in the case of acrylamide, N-alkylacrylamide,or N,N-dialkylacrylamide.

It is believed that the nitrogen-containing monomer enhances thecompatibility of the blend through association with the phenyl groups ofthe styrene blocks and/or the carboxyl groups of the polydiene orhydrogenated polydiene block, resulting in improved properties.

In a preferred embodiment, the homopolymer of the acrylic or methacrylicacid ester has a T_(g) less than 20° C. A polymeric moiety having aT_(g) greater than 20° C., a weight average molecular weight above2,000, and capable of associating with one or more of the blocks of theblock copolymer (e.g., a polystyryl moiety as described in Groves, U.S.Pat. No. 5,143,972 entitled "Pressure-Sensitive Adhesive Composition"which is hereby incorporated by reference) may be polymerized with theacrylic or methacrylic acid ester portions of the polymer. In this case,further association is believed to occur between this polymeric moietyand the phenyl groups of the styrene blocks.

Polymer (b) is preferably prepared by free radical-initiatedphotopolymerization or thermal polymerization of the base monomers usingconventional polymerization techniques. The resulting polymer is thenphysically blended with modified block copolymer (a).

Block copolymer (a) is present in an amount sufficient to allowassociation with the substrate, particularly if the substrate is a lowenergy substrate. Polymer (b) is present in an amount sufficient toassociate with block copolymer (a). The term "association" or"associate" as used herein with respect to the interaction between asubstrate and block copolymer (a) refers to the bonding or contactbetween the substrate and block copolymer (a) such that the substrate,particularly a low energy substrate, is made more receptive to materialssuch as inks; paints; and adhesives. That is, block copolymer (a), andultimately polymer (b) create an energy gradient between the substrateand a higher energy material, for example, an adhesive and/or paint,which is to be bonded to the substrate. The term "association" or"associate" as used herein with respect to polymer (b) and blockcopolymer (a) refers to the bonding or contact between polymer (b) andblock copolymer (a) such that each interacts with the other. The ratioof block copolymer (a) to polymer (b), by weight, preferably ranges fromabout 95:5 to about 5:95, more preferably from about 75:25 to about25:75.

Examples of preferred polymer blends include: (1) a blend of maleatedstyrene-ethylene/butylene-styrene block copolymer and iso-octylacrylate/N-vinylcaprolactam/acrylic acid polymer; (2) a blend ofmaleated styrene-ethylene/butylene-styrene block copolymer and iso-octylacrylate/N-vinylcaprolactam polymer; (3) a blend of maleatedstyrene-ethylene/butylenestyrene block copolymer and iso-octylacrylate/N-vinylcaprolactam/acrylic acid/acrylamide/polystyrene macromerpolymer; and (4) a blend of maleated styrene-ethylene/butylene-styreneblock copolymer and iso-octyl acrylate/acrylamide polymer. The blend maybe provided in the form of a primer and/or a paint, ink, or adhesive(e.g., a pressure sensitive adhesive) by using additives, for example,as described below.

As a primer, the polymer blend is particularly useful in the case of lowenergy substrates. As used herein, "low energy substrate" refers to asubstrate having a critical surface tension of wetting no greater thanabout 35 dynes/cm. Examples include polyolefin polymers such aspolyethylene and polypropylene.

The blends can be tackified by incorporating a tackifying agent,modifying the structure of the acrylate or methacrylate ester-containingpolymer, or through a combination of both. Tackifiers suitable fortackifying the blends include low molecular weight hydrocarbon resins,and α- and β-pinene based resins. Many tackifiers are commerciallyavailable, and optimum selection thereof can be accomplished by one ofordinary skill in the adhesive compounding art. Representative examplesof commercially available tackifiers suitable for the blends include theresins available under the trade designations "Regalrez 1018," "Regalfez1078," and "REZ-D 2084," all of which are available from Hercules Inc.,Wilmington, Del.; "Escorez-143H" and "Escorez 5380," both of which areavailable from Exxon Corp., Houston, Tex.; and "Wingtack Plus,"available from Goodyear Tire and Rubber Company, Akron, Ohio. The amountof tackifier included in the blend preferably ranges from about 20 toabout 250 parts per hundred parts of the blend. In general lowerconcentrations of tackifier are used where the blend is in the form of aprimer, whereas higher concentrations are used where the blend is in theform of a pressure sensitive adhesive.

The blends may include an anti-oxidant to inhibit oxidation of thetackifying agent and consequent loss of tackiness as the blends age.Suitable anti-oxidants are based on either (1) a hindered phenol or (2)a sulfur-containing organo-metal salt. Examples of hindered phenolsinclude ortho-substituted or 2,5-disubstituted phenols where thesubstituent group or groups is a branched hydrocarbon radical having 2to 30 carbon atoms, e.g., tertiary butyl or tertiary amyl radicals.Other hindered phenols useful in practicing the invention includepara-substituted phenols where the substituent groups are OR¹, where R¹is methyl, ethyl, 3-substituted propionic ester, etc. Examples ofcommercially available hindered phenols include those available fromCiba-Geigy Corp., Hawthorne, N.Y., under the trade designation "Irganox1076" and those available from American Cyanamid Company, Wayne, N.J.,under the trade designation "Cyanox LTDP." Suitable sulfur-containingorgano-metal salts are the nickel derivatives of dibutyldithiocarbamate.

The blends may further include inorganic fillers such as calciumcarbonate, clay, talc, silica, and limited amounts of carbon black, aswell as organic fillers such as wood flour and starch. Calciumcarbonates, clays, and talcs are most commonly used. The blends can alsobe colored by including dry pigments or color concentrates (usuallypolystyrene based); coloring is of ten desired where the blends are inthe form of paints or inks. Typical pigments include titanium dioxideand carbon black. Stabilizers such as fungicides and mildewicides can beincluded as well.

Other additives which may be included in the blends are silanes,titanates, and chlorinated polyolefins ("CPOs"). Furthermore resins suchas epoxy resins, may be blended with the block copolymer and acrylatepolymer.

The resistance to ultraviolet light degradation of the blends can beenhanced by incorporating ultraviolet inhibitors into the blends.Typically, a 1 part per hundred (phr) loading of the ultravioletinhibitor having the trade designation "Cyasorb IV 531" (available fromAmerican Cyanamid Company, Wayne, N.J.) or a mixture of equal parts ofultraviolet inhibitors having the trade designations "Tinuvin 328"(available from Ciba-Geigy Corp., Hawthorne, N.Y.) and "Uvinal 400"(available from GAF Corp., New York, N.Y.) is sufficient to provide thisenhancement. Enhanced results may be achieved from a combination of 0.5phr of one of the three above-mentioned ultraviolet inhibitors with anickel chelate having one of the following trade designations: "CyasorbUV 1084" (0.5 phr) (available from American Cyanamid Company, Wayne,N.J.) or "NBC" (0.1 phr) (available from E. I. du Pont de Nemours andCompany, Wilmington, Del.). As used herein, phr is based on the weightof block copolymer in the blend unless otherwise noted.

The above-described blends are particularly useful as primers foradhesives, e.g., pressure sensitive adhesives, thermo setting adhesives,thermoplastic adhesives, and hybrid adhesives. The term "hybridadhesives" as used herein refers to combinations of two or moredifferent types of adhesives as well as two or more polymers suitablefor forming adhesives.

Thermosetting adhesives are generally formed by addition polymerization.Examples of thermosetting adhesives include polysulfides, silicones,polyesters, polyurethanes, epoxies, anaerobic and aerobic acrylics,radiation curable polymers, and vulcanizing rubbers. Thermosettingadhesives typically cure by heat, catalysts, or light or moistureactivation. After curing, thermosetting adhesives are generallyinsoluble, i.e., the adhesive will not dissolved in an organic solventor water and infusible, i.e., the adhesive will not flow when heated.

Pressure sensitive adhesives generally do not undergo a progressiveincrease in viscosity after preparation, rather they are permanently ina tacky stage. Examples of pressure sensitive adhesive include thosederived from polyacrylates, block copolymers as defined herein, andnatural or synthetic rubber. Pressure sensitive adhesives typicallypossess viscoelastic properties and thus exhibit characteristics of botha viscous liquid and an elastic solid.

Thermoplastic adhesives are soluble and fusible materials. Examples ofthermoplastic adhesives include vinyl adhesives, e.g., polyvinylchloride, polyvinyl butyral, polyvinyl alkyl esters and ethers, andvinyl-acetate-ethylene copolymer adhesives; acrylic adhesives; hot meltadhesives; cellulosic adhesives; and asphalt adhesives. Thermoplasticadhesives may be in the form of emulsions, solutions, or solids.

A primer of the present invention may be applied using a variety oftechniques including dipping, spraying, brushing, rotogravure, Meierrod, and knife coating. One particularly useful application techniqueinvolves applying a primer of the present invention to the substrate andthen abrading. This technique effects chemical reactions induced bymechanical actions like abrading, i.e., mechanochemistry. Suitableabrasive products include a lint-free tissue, cloth, or sandpaper. Whensandpaper is used, it is preferably wet or dry and 50% of the abrasivegrit size preferably ranges from 100 to 2 microns. When pressuresensitive adhesives are being bonded to a substrate, preferably theabrasive grit size ranges from 8 to 2 microns, most preferably from 5.5to 2.0 microns. When structural adhesives, i.e., epoxies andpolyurethanes, are being bonded to a substrate, preferably the abrasivegrit size ranges from 100 to 50 microns.

The following non-limiting examples further illustrate the presentinvention. All percentages are in percentage by weight unless indicatedotherwise.

EXAMPLES TEST METHODS

A. PRIMERS

FPL Process For Etching Aluminum

Aluminum specimens (typically 152.4 mm×50.8 mm×1.6 mm specimens,(available from Vincent Metals, Minneapolis, Minn., under the tradedesignation "2024-T3 Alclad") are treated according to the etchingprocess described in H. W. Eichner, Forest Products Laboratory; ReportNo. 1842, Apr. 1, 1954, Madison, Wis., USA. Specifically, the specimensare treated as follows. Each specimen is rinsed in acetone and thenallowed to air dry. Next, each specimen is degreased by soaking for 10minutes in 75 g of Oakite 164 (alkaline detergent) per liter ofdistilled water. Each specimen is then rinsed for 2 minutes in tapwater, followed by immersion for 10 minutes at 71° C. in an etching bathconsisting of 1161 g of H₂ SO₄, 156.8 g of Na₂ Cr₂ O₇ 2H₂ O, 1.5 g of202H-T3 bare aluminum alloy chips, and enough distilled water to make3.5 liters of solution. Following immersion in the etching solution,each specimen is rinsed for 2 minutes with tap water and dried for 10minutes at 66° C.

Static Shear

The shear strength of primed and unprimed substrates bonded todouble-coated, pressure sensitive adhesive foam tapes or pressuresensitive transfer adhesives is determined according to the followingprocedure.

An FPL-etched aluminum strip (available from Vincent Metals,Minneapolis, Minn., under the trade designation "2024 -T3 Alclad")measuring 50.8 mm×25.4 mm×1.6 mm with a 7 mm diameter hole on center and10 mm from one edge of the strip is prepared. Likewise, similar stripsof the primed and unprimed substrate, each having a thickness that doesnot yield at the test temperature under the testing load, are prepared.

A 12.7 mm wide pressure sensitive adhesive tape carried on a releaseliner is adhered to the solid end of the aluminum strip (i.e., the endopposite the end with the hole) and trimmed to a length of 25.4 mm. Theliner is then removed and the solid end of the substrate strip adheredto the exposed adhesive surface. The resulting specimen is placed in ahorizontal position and rolled down with a 2.4 kg roller to insureintimate contact between the surfaces. After being kept at roomtemperature for 24 hours the specimen is placed in an air circulatingoven preheated to 80° C. After 15 minutes, a 1 kg weight is hung fromthe specimen. The specimen is tilted 2° from the vertical in order tonegate any peel forces. The time it takes for the weight to fall (inminutes) is the "static shear value". If no failure occurs after 6,000minutes, the test is discontinued.

90° Peel Adhesion- Pressure Sensitive Adhesive

Peel adhesions (N/100 mm) of double-coated pressure sensitive foam tapesto various primed and unprimed substrates are determined in thefollowing manner.

The matted side of a 114 mm×15.9 mm×0.13 mm piece of aluminum foil(1145-0-SB, Lawrence Fredrick Company, Greenwood, Ill.) is placed on thelinerless side of a foam tape sample carried on a release linermeasuring 101.6 mm×12.5 mm×1.1 min. A 2.4 kg hard rubber-covered steelroller is then passed back and forth three times over the specimen.

Next, about 50 mm of the liner is cut from the linered side of thesample, and the sample is then placed and centered near one end of a152.4 mm×50.8 mm×5.1 mm plaque of the primed or unprimed substrate. A2.4 kg hard rubber-covered roller is again passed back and forth threetimes over the assembled specimen. The procedure is then repeated tolaminate a second foam tape-aluminum construction to the other end ofthe plaque.

After dwelling for the specified length of time at ambient temperature,the specimen is placed in a 90° peel fixture (PJ-90, Consultants INTL.Network, Mentor, Ohio) and mounted in an Instron tensile tester(available from Instron Corp., Canton, Mass.). The 90° peel adhesion ismeasured by removing the free end of the aluminum foil-laminated foamtape at a rate of 30.5 cm per minute. The reported peel strengths (inN/100 mm) are an average of three determinations.

90° Peel Adhesion--Thermosetting Adhesive

Peel adhesions (N/100 mm) of films of polypropylene (PP) and low densitypolyethylene (LDPE) bonded with thermosetting adhesives are determinedin the following manner.

A film sample, 175 mm×75 mm×0.25 mm, was secured to a flat surface usinga 0.25 mm acrylic pressure sensitive transfer adhesive (available fromMinnesota Mining and Manufacturing Company, St. Paul, Minn. under thetrade designation "F9473PC"). The surface of the sample was flooded witha primer solution and evenly abraded with a piece of 80 micron grit,fabric backed abrasive (available from Minnesota Mining andManufacturing Company, St. Paul, Minn. under the trade designation"3M-ITE P220"). After one minute, the surface was flooded again withprimer solution and abraded for an additional one minute. The filmsample was washed three times each with xylene and ethanol and driedunder ambient conditions for 24 hours. A 0.5 mm layer of a two-partepoxy adhesive (available from Minnesota Mining and ManufacturingCompany, St. Paul, Minn. under the trade designation "Scotch-Weld 2216B/A") was applied to a 152.4 m×101.6 mm×1.6 mm FPL-etched 2024-T3aluminum panel. The primed side of the film was bonded to the adhesiveusing pressure from a light rubber-covered roller. After 72 hours, thefilm was slit into three 12.5 mm test specimens. The aluminum panel wasplaced in a 90° peel fixture (available from Consultant INTL Network,Mentor, Ohio) and mounted in an Instron tensile tester (available fromInstron Corp., Canton, Mass.). The 90° peel adhesion was measured byremoving the free end of the film strips at a rate of 30.5 cm perminute. A control sample was prepared in the same manner except thesample was not flooded with primer solution and the sample was abradedin the absence of a primer solution. The reported peel strengths (N/100mm) are an average of three determinations.

Cohesive Strength

The cohesive strengths of commercially available foam tapes weredetermined according to the procedure of the 90° peel adhesive test,except that the tapes were bonded to a 152.4 mm×50.8 mm×1.6 mm,FPL-Etched 2024-T3 aluminum panel and allowed to dwell for 2 hours priorto testing. The foam tapes were foam tapes available from MinnesotaMining and Manufacturing Company, St. Paul, Minn., under the tradedesignation "Scotch" in conjunction with the following designations"Y-4220", "VHB-4205", and "VHB-4950" (double coated with acrylicpressure sensitive adhesives); "VHB-4952" (double-coated with astyrene-butadiene rubber (SBR) pressure sensitive adhesive); and"VHB-4910" (1 mm thick acrylic transfer tape). All foam tapes failed bycohesive failure of the foam core. The results shown in Table A are anaverage of three values for each tape. These values are used asbenchmarks for the semi-quantitative peel adhesion test described below.

                  TABLE A                                                         ______________________________________                                        Tape Type Adhesive Type                                                                             Cohesive Failure (N/100 mm)                             ______________________________________                                        "Y-4220"  Acrylic     438                                                     "VHB-4205"                                                                              Acrylic     1050                                                    "VHB-4952"                                                                              SBR         658                                                     "VHB-4910"                                                                              Acrylic     702                                                     "VHB-4950"                                                                              Acrylic     877                                                     ______________________________________                                    

Semi-Quantitative Peel Adhesion

The level of adhesion of primed and unprimed substrates to pressuresensitive adhesives which cannot be determined quantitatively (e.g.,where the substrate is a thin and/or flexible film or a predimensionedrigid article) are determined semi-quantitatively. Sample preparation iscarried out according to the 90° peel adhesion procedure except that twoor more foam tapes are used and the tape-aluminum foil laminate issecured to the substrate with hand pressure or a 2.4 kg rubber-coveredsteel roller. After dwelling for a specified time (typically 15minutes), the free end of the tape-aluminum foil laminate is pulled fromthe substrate by hand. If cohesive failure of the foam core is notobserved, a foam tape having the next lowest cohesive strength(determined with reference to Table A, above) is bonded and thenremoved. This procedure is repeated with successive foam tapes (withreference to Table A, above) until cohesive failure of the foam coreoccurs. A semi-quantitative level of adhesion of the primed substrate tothe pressure sensitive adhesive of the foam tape is then determined withreference to Table A.

Single Overlap Shear

Two substrate plaques, each measuring 51 mm×25.4 mm×5 mm, are cleanedtwice with a heptane-saturated soft tissue and then rinsed with ethanol.After 15 minutes, the primer solution is applied to one side of each ofthe plaques using a cotton-tipped applicator and allowed to dry for 30minutes. Two drops of ethyl cyanoacrylate adhesive (available fromMinnesota Mining and Manufacturing Company, St. Paul, Minn., under thetrade designation "Pronto CA-40") are then placed on one of the primedsurfaces. Next, the remaining primed substrate plaque is placed on topof the cyanaoacrylate-containing plaque to form a 12.7 mm overlap joint.Finger-tight pressure is maintained over the joint for about 0.5minutes. Three test assemblies are prepared for each measurement andallowed to cure for 72 hours prior to testing. Joint strength ismeasured in an Instron tensile tester (available from Instron Corp.,Canton, Mass.) at a crosshead speed of 1.47 mm/min.

B. PRESSURE SENSITIVE ADHESIVES

The test methods used to evaluate the parameters of flexible sheetmaterials coated with pressure sensitive adhesive compositions accordingto the invention are standard industrial tests. The standard tests aredescribed in detail in various publications of the American Society forTesting and Materials (ASTM), Philadelphia, Pa. and the PressureSensitive Tape Council (PSTC), Glenview, Ill. The standard test methodsare described in detail below. The reference source of each of thestandard test methods is also given.

Shear Strength

Reference: ASTM:D3654-78; PSTC-7

The shear strength is a measure of the cohesiveness or internal strengthof an adhesive. It is based upon the amount of force required to pull anadhesive strip from a standard flat surface in a direction parallel tothe surface to which it has been affixed with a definite pressure. It ismeasured in terms of time (in minutes) required to pull a standard areaof adhesive-coated sheet material from a stainless steel test panelunder stress of a constant, standard load.

The tests are conducted on adhesive coated strips applied to a stainlesssteel panel such that a 12.5 mm by 12.5 mm portion of each strip is infirm contact with the panel, with one end portion of the tape beingfree. The panel with coated strip attached is held in a rack such thatthe panel forms an angle of 178° with the extended free end of the tapewhich is then tensioned by application of a force of one kilogramapplied as a hanging weight from the free end of the coated strip. The2° less than 180° is used to negate any peel forces, thereby insuringthat only the sheer forces are measured in an attempt to more accuratelydetermine the holding power of the tape being tested. The time elapsedfor each tape example to separate from the test panel (in minutes) isrecorded as the shear strength.

180° Peel Adhesion

Reference: ASTM: D3330-78; PSTC-1 (11/76)

Peel adhesion is the force required to remove a coated flexible sheetmaterial from a test panel measured at a specific angle and rate ofremoval. In the examples, this force is expressed in Newtons per 100 mm(N/100 mm) width of coated sheet. The measurement procedure is asfollows.

(1) A 12.5 mm width of coated sheet is applied to the horizontal surfaceof a clean glass test plate with at least 12.7 lineal cm in firmcontact. A hard rubber roller is used to apply the strip.

(2) The free end of the coated strip is doubled back nearly touchingitself so the angle of removal will be 180° . The free end is attachedto the adhesion tester scale.

(3) The glass test plate is clamped in the jaws of a tensile testingmachine which is capable of moving the plate away from the scale at aconstant rate of 2.3 meters per minute.

(4) The scale reading in Newtons is recorded as the tape is peeled fromthe glass surface. The data is reported as the range of numbers observedduring the test.

Inherent Viscosity

The inherent viscosity is measured by conventional means using aCannon-Fenske #50 viscometer in a water bath controlled at 25° C. tomeasure the flow time of 10 ml of polymer solution (0.15 g of polymerper deciliter of ethyl acetate). The examples and control examples beingrun for comparison were run under identical conditions.

A. PRIMERS

EXAMPLE 1

This example illustrates one preferred blend according to the inventionuseful as a primer.

Preparation of Block Copolymer Solution

A 25% solution of block copolymer was prepared by dissolving 25.0 g ofstyrene-ethylene/butylene-styrene triblock copolymer containing 2% boundsuccinic anhydride (available from Shell Chemical Company, Houston,Tex., under the trade designation "Kraton FG-1901X") and 0.25 g ofantioxidant (available from Ciba-Geigy Corp., Hawthorne, N.Y., under thetrade designation "Irganox 1076") in 75.0 g of a solvent mixture ofcyclohexane, xylene, and ethanol in a weight ratio of 5.5:3.5:1.0.

Preparation of Acrylate Ester Polymer

A terpolymer consisting of iso-octyl acrylate/N-vinylcaprolactam/acrylicacid (IOA/NVC/AA) in a weight ratio of 78:20:2 was prepared as follows.

To a 237 ml narrow-mouthed bottle were added 39 g of IOA, 10 g of NVC, 1g of AA, 0.1 g azobisisobutyronitrile (available under the tradedesignation "VAZO-64," from E. I. du Pont de Nemours & Company,Wilmington, Del.), 52.5 g of ethyl acetate, 9.0 g of methyl isoamylketone, and 13.5 g of xylene. The resulting solution was purged with dryargon for three minutes and sealed. The sealed bottle was then tumbledin a rotating water bath at 55° C. for 24 hours. The percentage ofconversion was determined to be 99.1% by infrared spectrophotometricanalysis. The solution contained 40% solids and had a viscosity of about7500 cps. The inherent viscosity was determined to be about 0.72 dl/g.

Preparation of Blend

A blend of the block copolymer and acrylate ester polymer in a 1:3weight ratio at a total solids concentration of 3.0% was prepared bydissolving 1.0 g of the block copolymer solution prepared as describedabove and 1.9 g of the acrylate ester polymer solution prepared asdescribed above in 30.4 g of a solvent blend of cyclohexane, xylene, andethanol in a weight ratio of 5.5:3.5:1.0.

EXAMPLES 2-12

In a like manner, blends of the block copolymer prepared as described inExample 1 and various acrylate ester polymers were prepared in a 1:3weight ratio. The identities of the acrylate ester polymers are setforth in Table 1, below.

                  TABLE I                                                         ______________________________________                                        Example  Polymer Composition                                                  ______________________________________                                        2        IOA/NVC/AA (88/10/2)                                                 3        IOA/NVC/AA (83/15/2)                                                 4        IOA/NVC/AA (93/5/2)                                                  5        IOA/NVP/AA/ACM/PSM (71/20/1/1/7).sup.1                               6        IOA/ACM (95/5)                                                       7        IOA/NVC (95/5)                                                       8        IOA/NVC (90/10)                                                      9        IOA/NVC (85/15)                                                      10       IOA/NVC (80/20)                                                      11       IOA/DMACM/AA (78/20/2).sup.2                                         ______________________________________                                         .sup.1 ACM is acrylamide. PSM is 2polystyrylethyl methacrylate (weight        average molecular weight about 10,000 g/mol, prepared according to U.S.       Pat. No. 4,554,324; 52% solids in cyclohexane). NVP is Nvinylpyrrolidone.     .sup.2 DMACM is N,Ndimethylaceylamide.                                   

The blends prepared according to examples 1-11 were applied by brush to152 mm×51 mm×5 mm plaques of low density polyethylene (LDPE),polypropylene (PP) (both available from Precision Punch and Plastics,Minneapolis, Minn.), and a thermoplastic polyolefin (TPO) (availablefrom Himont USA, Inc., Lansing, Mich., under the trade designation "ETA3163"). After 10 minutes, aluminum foil-laminated foam pressuresensitive adhesive tape samples (1 mm thick acrylic pressure sensitiveadhesive foam tape available from Minnesota Mining and ManufacturingCompany, St. Paul, Minn., under the trade designation "VHB -4205") werebonded to the primed areas as described in the Test Method for 90° peeladhesion. After one hour, 90° peel values were determined; the valuesare reported in Table II as an average of three measurements. Controlpeel values were also determined for unprimed plaques. The results areshown in Table III.

                  TABLE II                                                        ______________________________________                                        90° Peel Values (N/100 mm)                                             Example   LDPE          PP     TPO                                            ______________________________________                                        Control   26.0        26.0     17.5                                           1         158.0       281.0    754.0*                                         2         158.0       281.0    667.0                                          3         158.0       281.0    719.0*                                         4         158.0       263.0    210.0                                          5         158.0       491.0    754.0*                                         6         175.0       315.0    631.0                                          7         175.0       123.0    88.0                                           8         175.0       333.0    421.0                                          9         175.0       316.0    561.0                                          10        175.0       316.0    719.0*                                         11        125.0       614.0    772.0*                                         ______________________________________                                         *Cohesive failure of the foam core                                       

The results in Table II demonstrate that using blends according to theinvention to prime low energy surfaces improve the adhesion of pressuresensitive adhesives to the surfaces.

EXAMPLE 12

The block copolymer solution prepared according to Example 1 and theacrylate ester polymer prepared according to Example 5 were each dilutedto 3% polymer solids using a solvent blend of cyclohexane, xylene, andethanol in a weight ratio of 5.5:3.5:1.0, and applied by brush topolypropylene (PP) and low density polyethylene (LDPE) test plaques asdescribed above. Peel values were determined as described above andcompared to the values for the block copolymer/acrylate ester polymerblend prepared according to Example 5 and reported in Table II. Theresults are shown in Table III.

                  TABLE III                                                       ______________________________________                                        90° Peel Values (N/100 mm)                                                               LDPE  PP                                                    ______________________________________                                        Block Copolymer     88.0    88.0                                              Acrylate Ester Polymer                                                                            24.0    70.0                                              Example 5 Blend     158.0   491.0                                             ______________________________________                                    

The results in Table III demonstrate that while the individual blendcomponents, when used alone, do not perform well as primers, high peeladhesions are obtained when they are blended together.

EXAMPLE 13

Blends containing the block copolymer prepared as in Example 1 and theacrylate ester polymer of Example 5 were prepared in weight ratios of1:3, 1:1, and 3:1, diluted to 3% polymer solids, and brushed on testplaques of thermoplastic polyolefin (TPO) as described above. Peelvalues were determined using tape "VHB-4205" as described in Example 1;the results are shown in Table IV.

                  TABLE IV                                                        ______________________________________                                        Blend Ratio  90° Peel (N/100 mm)                                       ______________________________________                                        1:3          702*                                                             1:1          684*                                                             3:1          702*                                                             ______________________________________                                         *cohesive failure of the foam core                                       

The results in Table IV demonstrate that a wide variety of blockcopolymer/acrylate ester polymer ratios yield effective primercompositions for low energy surfaces.

EXAMPLE 14

The blend prepared according to Example 10 was applied to polypropylene(PP) and low density polyethylene (LDPE) test plaques using a lint-freetissue. After 10 minutes, aluminum foil-laminated foam tape were bondedto the primed substrates. In particular, the following tapes were used:double coated acrylic pressure sensitive adhesive foam tape (availablefrom Minnesota Mining and Manufacturing Company, St. Paul, Minn., underthe trade designation "VHB-4205"); 1 mm thick acrylic transfer pressuresensitive adhesive tape (available from Minnesota Mining andManufacturing Company, St. Paul, Minn., under the trade designation"VHB-4910"); double coated styrene-butadiene rubber pressure sensitiveadhesive foam tape (available from Minnesota Mining and ManufacturingCompany, St. Paul, Minn., under the trade designation "VHB-4952"). Afterone hour, 90° peel values were determined; values for unprimedsubstrates were determined as well. The results are reported in Table V.

                  TABLE V                                                         ______________________________________                                        90° Peel Values (N/100 mm)                                                            PP   LDPE                                                      ______________________________________                                        Unprimed                                                                      "VHB-4205"       26.0   26.0                                                  "VHB-4910"       52.0   26.0                                                  "VHB-4952"       298.0  210.0                                                 Primed                                                                        "VHB-4205"       350.0  772.0*                                                "VHB-4910"       210.0  439.0                                                 "VHB-4952"       421.0  702.0*                                                ______________________________________                                         *cohesive failure of the foam core                                       

The results in Table V demonstrate that the use of a blend according tothe invention as a primer improves the peel adhesion of both acrylic andstyrene butadiene rubber (SBR) pressure sensitive adhesives to lowenergy surfaces.

EXAMPLE 15

About 109 g of a 3% primer solution prepared according to Example 1 wasmodified by the addition of 0.5 g of epoxy resin (available from ShellChemical Company, Houston, Tex., under the trade designation "Epon828"), 3.0 g of chlorinated polypropylene (available from EastmanChemical Company, Kingsport, Tenn. under the trade designation "CP343-3"), 0.5 g of silane coupling agent (available from OSi Specialties,Danbury, Conn., under the trade designation "Silquest A 186"), and 0.8 gof triethanolamine titanate (available from E. I. du Pont de Nemours &Company, Wilmington, Del. under the trade designation "Tyzor TE"). About25 g of this solution was diluted to 1% solids by the addition of 109 gof a solvent mixture of cyclohexane, xylene, and ethanol in a weightratio of 5.5:3.5:1.0. The primer solution was brushed on test plaques ofglass, aluminum (Al), and stainless steel (S.S.). After 10 minutes,aluminum foil-laminated tapes (available from Minnesota Mining andManufacturing Company, ST. Paul, Minn. under the trade designations"VHB-4205", "VHB-4910", and "VHB-4952") were bonded to the primedsamples. After 72 hours, 90° peel values were determined; the resultsare recorded in Table VI.

COMPARATIVE EXAMPLE 15

The procedure of Example 15 was followed except that the glass,aluminum, and stainless steel test plaques were primed with acommercially available chlorinated polypropylene primer (available fromNorton Performance Plastics, Granville, N.Y., under the tradedesignation "Tite-R-Bond-2684"). The results are shown in Table VI.

                  TABLE VI                                                        ______________________________________                                        90° Peel Values (N/100 mm)                                             Primer Solutions                                                                              Glass       Al      S.S.                                      ______________________________________                                        Unprimed                                                                      "VHB-4205"      386          684*   315                                       "VHB-4910"      263         140     210                                       "VHB-4952"      386         386     351                                       Example 15                                                                    "VHB-4205"       701*        701*    772*                                     "VHB-4910"      649         439     368                                       "VHB-4952"      614          649*   561                                       Comparative Example 15                                                        "VHB-4205"       32         351      35                                       "VHB-4910"       26         351      17                                       "VHB-4952"      456         491      26                                       ______________________________________                                         *cohesive failure of the foam core                                       

Table VI demonstrates that the primer solution of this inventionimproves the adhesion of both acrylic and styrene butadiene rubber (SBR)pressure sensitive adhesives to substrates of high surface energy (e.g.,glass, stainless steel, and aluminum).

EXAMPLE 16

A 1% primer solution prepared according to Example 15 was applied to lowdensity polyethylene (LDPE) and polypropylene (PP) test plaques with alintless tissue (available from Kimberly-Clark Corp., Roswell, Ga.,under the trade designation "Kimwipe"). After 10 minutes, aluminumfoil-laminated tapes (available from Minnesota Mining and ManufacturingCompany, St. Paul, Minn. under the trade designations "VHB-4205","VHB-4910", and "VHB-4952") were bonded to the primed samples aspreviously described. After one hour the peel values were determined;the results are set forth in Table VII.

COMPARATIVE EXAMPLE 16

The procedure of Example 16 was followed except that the LDPE and PPtest plaques were primed with a commercially available chlorinatedpolypropylene primer (available from Norton Performance Plastics,Granville, N.Y., under the trade designation "Tite-R-Bond-2684"). Theresults are shown in Table VII.

                  TABLE VII                                                       ______________________________________                                        90° Peel Values (N/100 mm)                                                               LDPE  PP                                                    ______________________________________                                        Unprimed                                                                      "VHB-4205"           26      26                                               "VHB-4910"           26      52                                               "VHB-4952"          210     298                                               Example 16                                                                    "VHB-4205"           789*    824*                                             "VHB-4910"          596     421                                               "VHB-4952"           702*   526                                               Comparative Example 16                                                        "VHB-4205"          298     473                                               "VHB-4910"          140     351                                               "VHB-4952"          351     403                                               ______________________________________                                         *cohesive failure of the foam core                                       

Table VII demonstrates that the primer solution of Example 16 improvesthe adhesion of both acrylic and styrene butadiene rubber (SBR) pressuresensitive adhesives to substrates of low surface energy.

EXAMPLE 17

A 1% primer solution prepared according to Example 15 was brushed onmm×75 mm×0.25 mm specimens of linear low density polyethylene film(LLDPE) (available from Consolidated Thermoplastics Company, Schaumburg,Ill.). After 15 minutes, aluminum foil-laminated foam tape samples(available from Minnesota, Mining and Manufacturing, St. Paul, Minn.,under the trade designations "VHB-4220" and "VHB-4205") were bonded tothe primed samples. After one hour, semi-quantitative peel adhesionswere measured by attempting to remove the tapes by hand. Samples of"VHB-4220" could not be removed due to cohesive failure of the foamcore. This indicated peel adhesion values of at least 425 N/100 mm hadbeen achieved.

Although excellent adhesion of the "VHB-4205" foam tape was observed, itcould be removed from the primed LLDPE without cohesive foam failure.After 12 hours, cohesive foam failure was observed, indicating that apeel value of about 1000 N/100 mm had been achieved.

COMPARATIVE EXAMPLE 17

The procedure of Example 17 was followed except that a commerciallyavailable chlorinated polypropylene primer (available from NortonPerformance Plastics, Granville, N.Y., under the trade designation"Tite-R-Bond 2684") was brushed on the LLDPE specimens. After 15minutes, foam tape (available from Minnesota Mining and ManufacturingCompany, St. Paul, Minn., under the trade designation "VHB-4220") wasbonded to the samples. After intervals of both one and twelve hours, thetape could easily be removed by hand. Peel values were estimated to beonly about 90 N/100 mm or less.

EXAMPLE 18

A 1% primer solution prepared according to Example 15 was brushed on two125 mm×75 mm×0.25 mm specimens of LLDPE film following the procedure ofExample 17. The primed specimens were then allowed to dry for 15 minutesand 24 hours, respectively. Next, the primed samples were painted with alatex semi-gloss interior enamel (available from The Glidden Company,Cleveland, Ohio), an interior/exterior oil-based high gloss enamel(available from Carver Tripp, Parks Corp. Somerset, Mass.), and anaerosol polyurethane lacquer (available from Minnesota Mining andManufacturing Company, St. Paul, Minn., under the designation PartNO-05904). In a like manner, unprimed specimens of LLDPE film were alsopainted. After drying under ambient conditions for 24 hours, 125 mm×75mm×0.25 mm samples of filament tape (available from Minnesota Mining andManufacturing Company, St. Paul, Minn., under the trade designation"Scotch Brand 898") were firmly bonded to each painted surface (primedand unprimed). After 15 minutes, the tape was quickly removed from eachspecimen. Complete delamination of all paints to the unprimed LLDPEfilms was observed. No delamination of paint was observed from any ofthe primed LLDPE surfaces.

COMPARATIVE EXAMPLE 18

The procedure of Example 18 was followed except that a commerciallyavailable chlorinated polypropylene primer (available from NortonPerformance Plastics, Granville, N.Y., under the trade designation"Tite-R-Bond 2684") was brushed on LLDPE specimens. The primed specimenswere painted and tested as described in Example 18. Completedelamination of all paints to the primed film was observed.

EXAMPLE 19

To 10 g of a 3% primer solution prepared according to Example 15 wasadded 1 g of titanium dioxide dispersion (available from H uls AmericaInc., Piscataway, N.J., under the trade designation "GPD 82-0082").Likewise, to another 10 g of the same primer solution was added 1 g ofcarbon black dispersion (available from Borden Chemical Company,Cincinnati, Ohio, under the trade designation "Codispersion 31L62").After mixing, both pigmented solutions were brushed on untreated LLDPEfilm and allowed to dry at ambient conditions for 24 hours. The peeladhesion values of the pigmented coatings to LLDPE film were determinedby firmly bonding filament tape (available from Minnesota Mining andManufacturing Company, St. Paul, Minn., under the trade designation"Scotch Brand 898") to the coated surfaces in the manner previouslydescribed in Example 18. No delamination of either coating was observedwhen the tape was rapidly removed.

This example demonstrates that compositions according to the inventioncan be utilized to prepare coatings, inks, and paints that adhere wellto low energy polymer surfaces.

EXAMPLE 20

A 1% primer solution prepared according to Example 15 was brushed on50.8 mm×24.4 mm×5.1 mm test plaques of thermoplastic polyolefin (TPO)(commercially available from Himont USA Inc., Lansing, Mich., under thetrade designation "ETA 3163") and tested for static shear to FPL etched2024-T3 aluminum at 80° C. under a 1.0 kg load utilizing foam tape(available from Minnesota Mining and Manufacturing Company, St. Paul,Minn., under trade designation "VHB-4210"). Unprimed thermoplasticolefin (TPO) specimens were also tested. The results are reported inTable VIII.

                  TABLE VIII                                                      ______________________________________                                        Primer      Static Shear Value (min.)                                         ______________________________________                                        None        300                                                               Example 15  10,000 +                                                          ______________________________________                                    

The results in Table VIII demonstrate that the primer solutions of theinvention improve the high temperature holding power of an acrylicpressure sensitive adhesive to substrates of low surface energy.

EXAMPLE 21

A 3% primer solution prepared according to Example 15 was brushed onboth sides of a 150 mm×150 mm×0.10 mm specimen of clear, flexiblepolyvinyl chloride (PVC) film (available from Wiman Plastic Div., St.Cloud, Minn.) and a 150 mm×150 mm×0.35 mm specimen of unpigmented,opaque thermoplastic polyolefin (TPO) film (available from Himont USAInc., Lansing, Mich., under the trade designation "HIFAX CA10A") andallowed to dry for 30 minutes. A 0.25 mm acrylic pressure sensitivetransfer adhesive carried on a removable liner (available from MinnesotaMining and Manufacturing Company, St. Paul, Minn., under the designation"F 9473 PC") was laminated to one side of each of the films with a 2.4kg hard rubber roller. Likewise, 126 mm×12.5 mm of the same adhesive waslaminated to 130 mm×15.9 mm×0.13 mm strips of aluminum foil with a 2.4kg hard rubber roller.

The peel values of the transfer adhesive to the primed tape backingswere then determined by laminating a 150 mm×51 mm sample of eachtransfer tape/backing construction to 152 mm×51 mm×1.6 mm FPL etched,2024-T3 aluminum plates with a 2.4 kg rubber roller. About 75 mm ofliner was removed from the aluminum foil-laminated transfer adhesivesamples and bonded to each of the tape samples on the aluminum plate ina manner such that two test samples for each tape were prepared. Theresulting samples had the following construction: aluminumplate/transfer adhesive/primed backing (both sides)/transferadhesive/aluminum foil. Unprimed control samples were prepared in asimilar manner. The peel values are reported in Table IX.

                  TABLE IX                                                        ______________________________________                                                 Peel Values (N/100 mm)                                               ______________________________________                                        Unprimed                                                                      PVC        175                                                                TPO         7                                                                 Primed                                                                        PVC         702*                                                              TPO         702*                                                              ______________________________________                                         *adhesive and film failure                                               

This example illustrates that pressure sensitive adhesive tapes havingholding power to backing equivalent to the cohesive strength of theadhesive or the tensile or yield strength of the backing can beprepared.

EXAMPLE 22

Plaques measuring 51 mm×25.4 mm×5 mm of polypropylene (PP) and highdensity polyethylene (HDPE) (available from Precision Punch & Plastics,Minneapolis, Minn.) were cleaned with heptane and rinsed with ethanol.After 15 minutes a 1% primer solution prepared according to Example 15was applied to one side of each of the plaques using a cotton-tippedapplicator. The primed plaques were then bonded together with ethylcyanoacrylate adhesive and the overlap joint strengths determined. Theresults are reported in Table X.

                  TABLE X                                                         ______________________________________                                        Substrate Overlap Joint Strength (N/mm.sup.2)                                 ______________________________________                                        HDPE      2.5                                                                 PP        4.6                                                                 ______________________________________                                    

This example illustrates that the primer solutions of the inventioninitiate the polymerization of ethyl cyanoacrylate adhesives to givehigh bond strengths between substrates of low surface energy.

EXAMPLE 23

A construction using a thermosetting adhesive was prepared as describedunder 90 Peel Adhesion--Thermosetting Adhesive test method. The 5%solution set forth in Table XI was used.

                  TABLE XI                                                        ______________________________________                                        Component                  Amount (g)                                         ______________________________________                                        solvent mixture of cyclohexane, xylene, and ethanol                                                      30                                                 in a weight ratio of 5.5:3.5:10                                               styrene block copolymer (available from Shell                                                            0.23                                               Chemical Company, Houston, TX under the trade                                 designation "FG 1901X")                                                       chlorinated polypropylene (available from Eastman                                                        0.92                                               Chemical, Kingsport, TN under the trade                                       designation "CP 343-3")                                                       epoxy resin (available from Shell Chemical                                                               0.15                                               COmpany, Houston, TX, under the trade                                         designation "Epon 828")                                                       epoxy silane coupling agent (available from OSi                                                          0.15                                               Specialties Inc., Danbury, CT, under the trade                                desgination "Silquest A 186")                                                 iso-octyl acrylate/N-vinylcaprolactam/acrylic acid                                                       1.8                                                polymer in a weight ratio of 78:21:1 (40% solids)                             triethanolamine titanate (available from E. I. du Pont                                                   0.07                                               de Nemours & Company, Wilmington, DE, under                                   the trade designation "Tyzor TE")                                             ______________________________________                                    

The surface of the sample was initially flooded with about 1.5 ml of thesolution and abraded according to the test method described above. Thecontrol sample was abraded in the absence of primer solution. Theresults are set forth in Table XII.

                  TABLE XII                                                       ______________________________________                                                       90° Peel Values (N/100 mm)                              Solution         LDPE    PP                                                   ______________________________________                                        Control          17.5    14.0                                                 Example 23       163.0   502*                                                 ______________________________________                                         *film failure, i.e., the strength of the film was exceeded and the film       has changed dimensions                                                   

The 90° peel values were dramatically increased by using a solution inaccordance with the present invention as compared to an unprimedsubstrate.

EXAMPLE 24

Thermoplastic polyolefin plaques, 51 mm×25.4 mm×5 mm, (available fromHimont USA, Inc., Lansing, Mich., under the trade designation "ETA3163") were cleaned twice with ethanol and allowed to dry. A 5% solutionprepared according to Example 23 was brushed on one side of each of theplaques and allowed to dry for 24 hours.

The primed plaques were bonded with two-part epoxy adhesives (availablefrom Minnesota Mining and Manufacturing Company, St. Paul, Minn., underthe trade designation "Scotch-Weld 2216 B/A") to form 25.4 mm×12.7 mmoverlap joint. The samples were allowed to cure for 72 hours under aweight of 150 g. A control sample was prepared without using any primersolution. Joint strengths (N/mm²) were measured in an Instron tensiletester (available from Instron Corp., Canton, Mass.) at a crossheadspeed of 12.7 mm per minute. The values reported in Table XIII are anaverage of three determinations for Example 24 and a singledetermination for the control sample

                  TABLE XIII                                                      ______________________________________                                                   Overlap Joint Strength (N/mm.sup.2)                                Solution   TPO                                                                ______________________________________                                        Control    0.34                                                               Example 24 1.65                                                               ______________________________________                                    

B. PRESSURE SENSITIVE ADHESIVES

EXAMPLE 25

This example illustrates one preferred blend according to the inventionuseful as a pressure sensitive adhesive.

The following ingredients in the amounts shown were introduced into aone liter jar.

    ______________________________________                                                                    Amount                                            Ingredient                  (g)                                               ______________________________________                                        Maleated styrene-ethylene/butylene-styrene elastomer                                                      100                                               (available from Shell Chemical Company, Houston, TX,                          under the trade designation "Kraton FG 1901X")                                Tackifier (available from Hercules Inc., Wilmington, DE,                                                  75                                                under the trade designation "Regalrez 1018")                                  Tackifier (available from Hercules Inc., Wilmington, DE,                                                  75                                                under the trade designation "Rez-D 2084")                                     Tackifier (available from Hercules Inc., Wilmington, DE,                                                  25                                                under the trade designation "Regalrez 1078")                                  Antioxidant (available from Ciba-Geigy Corp., Hawthorne,                                                  1                                                 NY, under the trade designation "Irganox 1076")                               Antioxidant (available from American Cyanamid Company,                                                    1                                                 Wayne, NJ, under the trade designation "Cyanox LTDP")                         Ultraviolet inhibitor (available from Ciba-Geigy Corp.,                                                   0.3                                               Hawthorne, NY, under the trade designation "Tinuvin 328")                     Ultraviolet inhibitor (available from GAF Corp., New York,                                                0.3                                               NY, under the trade designation "Unvinal 400")                                Toluene                     323                                               Ethanol                     16.5                                              ______________________________________                                    

The jar was shaken until the ingredients dissolved to give a solutioncontaining about 45% total solids and a viscosity of about 1300 cps (asmeasured by a Brookfield viscometer, Model HAT, Spindle No. 4, Speed 50rpm). The solution is referred to herein as the "block copolymer."

43.3 g of the block copolymer was introduced into a 118 ml jar alongwith 26.2 g of an iso-octyl acrylate/acrylamide (IOA/ACM) copolymerprepared according to Example 6. The blend was stirred vigorously untilit was homogeneous. The jar was capped and heated at 65° C. for aboutone hour. The blend was then stirred vigorously and allowed to standovernight. The blend contained 65% by weight of the block copolymer and35% by weight of the IOA/ACM copolymer. After mild agitation, the blendwas coated onto oriented polyethylene terephthalate film having 0.025 mmthickness by means of a laboratory 52 mm knife coater at a knife settingof about 0.25 mm. The coated film was air dried at 95° C. for 15 minutesto give an average coating weight of about 6.0 mg/cm². Samples wereprepared according to Test Methods previously described and tested forpeel adhesion to glass, low density polyethylene (LDPE), polypropylene(PP), and stainless steel (SS) surfaces, and shear strength. The resultsare shown in Table XIV.

                  TABLE XIV                                                       ______________________________________                                        Peel Value (N/100 mm)                                                         Adhesive                                                                              Glass    LDPE     PP    SS    Shear(min.)                             ______________________________________                                        Example 23                                                                            68       29       52.5  61    220                                     ______________________________________                                    

The results of Table XIV demonstrate that useful pressure sensitiveadhesives can be prepared from blends according to the invention.

C. TIE LAYERS

EXAMPLE 26

A blend was prepared by combining 15 g of the block copolymer solutiondescribed in Example 1 and 30 g of the acrylate ester polymer describedin Example 1. The blend was combined with 1 g of epoxy resin (availablefrom Shell Chemical Company, Houston, Tex., under the trade designation"Epon 828"), 3.0 g of chlorinated polypropylene (available from EastmanChemical Company, Kingsport, Tenn. under the trade designation "CP343-3"), 2.5 g of silane coupling agent (available from OSi Specialties,Danbury, Conn., under the trade designation "Silquest A 186"), 4 g oftriethanolamine titanate (available from E. I. du Pont de Nemours &Company, Wilmington, Del. under the trade designation "Tyzor TE") and 99g of a solvent mixture of cyclohexane, xylene, and ethanol in a weightratio of 5.5:3.5:1.0 to prepare about an 18% solution.

This solution was cast onto the non-matted side of three 152.4 mm×24.5mm×1.3 mm aluminum strips (available from Lawrence Fredrick Company,Greenwood, Ill.). A 0.25 mm thick coating of the solution dried to formabout a 0.037 mm thick coating of adhesive on each strip.

A 3% primer solution prepared as described in Example 15 was brushedonto three 152.4 mm×24.5 mm×2.5 mm plaques of thermoplastic olefin(TPO), (available from Himont USA, Inc., Lansing, Mich., under thedesignation "ETA 3095") and allowed to dry. The adhesive-coated aluminumstrips were laminated to about 137 mm of the primed TPO plaques at atemperature of 200° C. for 15, 30, and 45 seconds, respectively, underlow pressure. Peel values were determined to be 175.4 N/100 mm, 245.6N/100 mm, and 265 N/100 mm, respectively.

This example illustrates the utility of the compositions of thisinvention as adhesive tie layers for laminating dissimilar materialstogether.

What is claimed is:
 1. A method of enhancing adhesion between asubstrate and an adhesive comprising the steps of:priming said substrateby applying to said substrate a blend comprising(a) a block copolymercomprising(i) a polystyrene block and (ii) a polydiene block or ahydrogenated polydiene block, said polydiene block or hydrogenatedpolydiene block containing an average of one or more carboxyl groups;and (b) a polymer comprising a polymerization reaction product of two ormore mono-ethylenically unsaturated monomers in which:(i) at least oneof the monomers is an acrylic or methacrylic acid ester of anon-tertiary alcohol having 1 to 14 carbon atoms, inclusive, and (ii) atleast one of the monomers is a nitrogen-containing monomer selected fromthe group consisting of an N-vinyllactam and an N,N-dialkylacrylamide;and applying an adhesive to the primed substrate.
 2. The method of claim1 wherein said substrate comprises a low energy substrate.
 3. The methodof claim 1 wherein said adhesive is selected from the group consistingof pressure-sensitive adhesives, thermosetting adhesives, thermoplasticadhesives, and hybrid adhesives.
 4. A method of priming a substratecomprising applying to the substrate a blend comprising(a) a blockcopolymer comprising(i) a polystyrene block and (ii) a polydiene blockor a hydrogenated polydiene block, said polydiene block or hydrogenatedpolydiene block containing an average of one or more carboxyl groups;and (b) a polymer comprising a polymerization reaction product of two ormore mono-ethylenically unsaturated monomers in which:(i) at least oneof the monomers is an acrylic or methacrylic acid ester of anon-tertiary alcohol having 1 to 14 carbon atoms, inclusive, and (ii) atleast one of the monomers is a nitrogen-containing monomer selected fromthe group consisting of an N-vinyllactam and an N,N-dialkylacrylamide.5. A method of priming a substrate comprising applying to the substratea blend comprising a maleated styrene-ethylene/butylene styrene blockcopolymer and an iso-octyl acrylate/N-vinylcaprolactam/acrylic acidpolymer.